11o (/1 T Q_ z o 100 4 90- 80- 70- 60- 50- 40- 30 20 10 A X 0 IA O0 O0 0 0 A 0 20 40 60 80 100 120 TIME (DAYS) 140 Figure 14. Sedimentation curves at 45øC. Emulsions contained 1% emulsifier and various xanthan gum concentrations. [] 0%, + 0.1%, O 0.2%, A 0.3%, x 0.4%. 2,5 -- - 2- o 1 - 0.5 - -0.5 -1 + o 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 POLYMER CONC. (% W/W) Figure 15. Effect of different polymers on creaming rate at 1% emulsifier concentration at 45øC. [] xanthan gum, d- sodium carboxymethylcellulose, O methylcellulose.

EMULSION STABILIZATION BY GUMS 349 lOO 90 80- 70- 50- 40 3o 2o Io + + + + + + + + 20 40 60 80 1 O0 120 TIME (DAYS) Figure 16. Sedimentation curves at room temperature. Emulsions contained 1% emulsifier, 0.2% xanthan gum, and various sodium sulfate concentrations. [] 0 M, + 0.1 M, O 0.2 M, /• 0.3 M. CONCLUSIONS Our results indicate that the major effect of the polymers studied in our emulsions was on bulk phase rheology. The creaming rate was especially sensitive to the nature and concentration of added polymer. There was some indication that oil separation under conditions of severe stress (high temperature storage and high salt concentration) was delayed, though not necessarily prevented, by polymer. The polymers studied differed in the effects they had on emulsion properties. Because rheology characteristics of the polymers varied in a qualitative as well as a quantitative sense, creaming rate was not a simple function of the viscosity measured at 3 rpm. Of the polymers tested, xanthan gum was highly effective at very low concentrations. Higher concentrations of sodium carboxymethylcellulose were needed to obtain essen- tially the same creaming rate, while methylcellulose was less effective and also less efficient in our emulsions. A final note concerning methodology seems warranted. Emulsions are so complex that it is impossible to characterize them with a single type of measurement. It is advisable to bring several techniques to bear and to interpret the results in view of the multiple information sources that have been utilized.